From: Andy Wingo <wingo@pobox.com>
To: Chris Vine <vine35792468@gmail.com>
Cc: guile-user@gnu.org, guile-devel@gnu.org
Subject: Re: GNU Guile 2.9.5 Released [beta]
Date: Tue, 07 Jan 2020 22:53:44 +0100 [thread overview]
Message-ID: <87r20b3pcn.fsf@pobox.com> (raw)
In-Reply-To: <20200106231419.7fd821d8a60f0ef400f7ffe1@gmail.com> (Chris Vine's message of "Mon, 6 Jan 2020 23:14:19 +0000")
On Tue 07 Jan 2020 00:14, Chris Vine <vine35792468@gmail.com> writes:
> I wonder if it would surprise the programmer to have the cond
> conditionals evaluated in a different dynamic environment from the one
> in which the cond consequential is evaluated where there is a
> conditional which is true.
I entirely agree it's not ideal and can be surprising! I am not sure
that there is an "ideal" here though; with-exception-handler is
wonderfully expressive but can be verbose, guard is a pleasant
abbreviation but how to deal with re-raising from the original context?
In the end, "guard" is just a macro over a more general facility. But
it's a macro that we expect people to use, and to cover the common case.
To that end I think we should make it cheap and avoid rewinding while
also preserving the nice characteristic of evaluating cond consequents
in the continuation of the "guard" itself.
Andy
prev parent reply other threads:[~2020-01-07 21:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-22 15:22 GNU Guile 2.9.5 Released [beta] Andy Wingo
2019-11-22 16:01 ` tomas
2019-12-01 20:41 ` Chris Vine
2020-01-05 20:15 ` Andy Wingo
2020-01-05 23:26 ` Chris Vine
2020-01-06 20:34 ` Andy Wingo
2020-01-06 23:14 ` Chris Vine
2020-01-07 21:53 ` Andy Wingo [this message]
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